Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs
Dissertation (Ph.D.) University of Alaska Fairbanks, 2022 Increased surface melt in the percolation zone of Greenland causes significant changes in the firn structure, directly affecting the surface mass balance of the ice sheet and the amount and timing of meltwater runoff. Thick impermeable layers...
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ftunivalaska:oai:scholarworks.alaska.edu:11122/13116 2023-05-15T16:26:48+02:00 Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs Covi, Federico Hock, Regine Tedesco, Marco Truffer, Martin Sturm, Matthew 2022-12 http://hdl.handle.net/11122/13116 en_US eng http://hdl.handle.net/11122/13116 Department of Geosciences Ice sheets Greenland Ice fields Firn Meltwater Runoff Ice-atmosphere interaction Doctor of Philosophy in Geophysics Dissertation phd 2022 ftunivalaska 2023-02-23T21:38:03Z Dissertation (Ph.D.) University of Alaska Fairbanks, 2022 Increased surface melt in the percolation zone of Greenland causes significant changes in the firn structure, directly affecting the surface mass balance of the ice sheet and the amount and timing of meltwater runoff. Thick impermeable layers, referred to as ice slabs, are preventing melt water percolation and refreezing in the firn favoring lateral movement of water and direct runoff to the oceans. The objective of this dissertation is to enhance the understanding of these processes by modeling the surface energy balance and resulting melt, and investigating the spatial and temporal changes in firn surface properties and associated water movement in the percolation zone in southwest Greenland. Extensive fieldwork was carried out in this region between 2017 and 2019, including a collection of 19 shallow firn cores at several sites and the operation of two weather stations. A surface-energy balance model was forced with automatic weather station data from two sites (2040 and 2360 m a.s.l.). Extensive model validation and sensitivity analysis reveal that the skin layer formulation used to compute the surface temperature by closing the energy balance leads to a consistent overestimation of melt by more than a factor of two or three depending on the site. The results indicate that the energy available for melt is highly sensitive to small changes in surface temperature and suggests caution is needed in modeling Greenland melt from weather data. Furthermore, the spatial and temporal variability in air temperature bias of two regional climate models, MAR and RACMO, is assessed over the entire ice sheet. Model results are compared to 35 automatic weather stations over more than 25 years. Both models perform well in the ablation zone (< 1500 m a.s.l.) where most of the melt happens. However, a warm bias is found in both MAR and RACMO at the higher elevations percolation zone (> 1500 m a.s.l.). The seasonal evolution and interannual variability of ... Doctoral or Postdoctoral Thesis Greenland Ice Sheet Alaska University of Alaska: ScholarWorks@UA Fairbanks Greenland |
institution |
Open Polar |
collection |
University of Alaska: ScholarWorks@UA |
op_collection_id |
ftunivalaska |
language |
English |
topic |
Ice sheets Greenland Ice fields Firn Meltwater Runoff Ice-atmosphere interaction Doctor of Philosophy in Geophysics |
spellingShingle |
Ice sheets Greenland Ice fields Firn Meltwater Runoff Ice-atmosphere interaction Doctor of Philosophy in Geophysics Covi, Federico Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs |
topic_facet |
Ice sheets Greenland Ice fields Firn Meltwater Runoff Ice-atmosphere interaction Doctor of Philosophy in Geophysics |
description |
Dissertation (Ph.D.) University of Alaska Fairbanks, 2022 Increased surface melt in the percolation zone of Greenland causes significant changes in the firn structure, directly affecting the surface mass balance of the ice sheet and the amount and timing of meltwater runoff. Thick impermeable layers, referred to as ice slabs, are preventing melt water percolation and refreezing in the firn favoring lateral movement of water and direct runoff to the oceans. The objective of this dissertation is to enhance the understanding of these processes by modeling the surface energy balance and resulting melt, and investigating the spatial and temporal changes in firn surface properties and associated water movement in the percolation zone in southwest Greenland. Extensive fieldwork was carried out in this region between 2017 and 2019, including a collection of 19 shallow firn cores at several sites and the operation of two weather stations. A surface-energy balance model was forced with automatic weather station data from two sites (2040 and 2360 m a.s.l.). Extensive model validation and sensitivity analysis reveal that the skin layer formulation used to compute the surface temperature by closing the energy balance leads to a consistent overestimation of melt by more than a factor of two or three depending on the site. The results indicate that the energy available for melt is highly sensitive to small changes in surface temperature and suggests caution is needed in modeling Greenland melt from weather data. Furthermore, the spatial and temporal variability in air temperature bias of two regional climate models, MAR and RACMO, is assessed over the entire ice sheet. Model results are compared to 35 automatic weather stations over more than 25 years. Both models perform well in the ablation zone (< 1500 m a.s.l.) where most of the melt happens. However, a warm bias is found in both MAR and RACMO at the higher elevations percolation zone (> 1500 m a.s.l.). The seasonal evolution and interannual variability of ... |
author2 |
Hock, Regine Tedesco, Marco Truffer, Martin Sturm, Matthew |
format |
Doctoral or Postdoctoral Thesis |
author |
Covi, Federico |
author_facet |
Covi, Federico |
author_sort |
Covi, Federico |
title |
Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs |
title_short |
Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs |
title_full |
Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs |
title_fullStr |
Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs |
title_full_unstemmed |
Processes in the percolation zone in southwest Greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs |
title_sort |
processes in the percolation zone in southwest greenland: challenges in modeling surface energy balance and melt, and the role of topography in the formation of ice slabs |
publishDate |
2022 |
url |
http://hdl.handle.net/11122/13116 |
geographic |
Fairbanks Greenland |
geographic_facet |
Fairbanks Greenland |
genre |
Greenland Ice Sheet Alaska |
genre_facet |
Greenland Ice Sheet Alaska |
op_relation |
http://hdl.handle.net/11122/13116 Department of Geosciences |
_version_ |
1766015784326266880 |